This invention relates to a buttonhole stitching device for sewing machine, and more particularly relates to a built-in buttonholer which which a buttonhole is stitched by one manual operation of the device while running the sewing machine after buttonhole stitching is selected. Namely when buttonhole stitching is selected, the sewing machine sews first bartack stitches and the leftside stitches of the buttonhole, and then when a manual operation is carried out, the sewing machine sews the second bartack stitches and the right-side stitches of the buttonhole.
The conventional buttonhole stitching devices are complex in operation and lack in practical utility. That is to say, in a sewing machine with a built-in pattern cam group, if the buttonhole stitching is interrupted when only partly completed and another pattern is selected, desired stitches can not be obtained for the pattern because the automatic stepping function of the button hole device remains operative.
In another example, when the button hole stitching has once been selected, a pattern selecting dial can no more be rotated, and it becomes impossible to select another pattern until one cycle of the button hole is completed. Therefore it becomes impossible to temporarily to stop the button hole stitching to reset the device to the first starting position of the buttonhole.
In another example, dials or buttons are provided for selecting a stitch pattern and a button hole stitch respectively, and the pattern selecting dial is normally located in the same position. Therefore it becomes necessary to select the button hole stitching with both hands.
Furthermore, there are also disadvantages in the pattern selecting devices provided in the conventional superposed cam built-in zig-zag sewing machines. That is, as a first system, two operating dials or buttons are provided, and a follower for releasing button is pushed with one hand's thumbs of one hand and in such a condition a follower for selecting patterns is moved with another hand's thumb to rotate a dial therefor, so-called "two hand control". The releasing button must continue to be pushed (heavily in general), and the selecting dial is often forcibly rotated by error when the follower is not released or not fully released.
For a second system the releasing dial is rotated to set the follower at the releasing position, and in the meantime another dial moves the follower. But handling is complicated and cancelling of the releasing condition of the follower is often forgotten.
A third system is that one dial is pushed or pulled to release the follower and the dial is rotated to select a desired cam while maintaining the releasing condition with the thumbs. Not only is the releasing operation rather difficult, but also the dial can be rotated, when the follower is not fully released, so that the sewing machine is damaged.
A fourth example is that releasing and selecting are carried out per one step only by rotation of one dial. Although operation is simple, the rotating angle of one step of the dial is naturally large since nowaday an automatic feed must release at least two followers of the lateral needle movement and the cloth feed, and if the roating angle is not large, the operation is different, since after the followers are released, they are moved and this releasing condition is cancelled. Therefore in many stored pattern cams, the rotating angle of the dial is considerably large and operation is poor.
As said, the conventional devices are accompanied with many disadvantages and lack in industrial or practical merits.